Pyrojet cutter for underwater or land use

ABSTRACT

1. An apparatus for burning through explosive containing cases and for melting out the enclosed explosive comprising a metal cylinder having a bore along the longitudinal axis thereof, said cylinder being externally-threaded at each of its ends; FIRST COMBUSTIBLE SOLID PROPELLANT MIXTURE WHICH BURNS TO PRODUCE A RELATIVELY HIGH-TEMPERATURE GASEOUS PRODUCT POSITIONED IN SAID BORE AT ONE END THEREOF; A SECOND COMBUSTIBLE SOLID PROPELLANT MIXTURE WHICH BURNS TO PRODUCE A RELATIVELY LOW-TEMPERATURE GASEOUS PRODUCT POSITIONED IN SAID BORE AT THE OTHER END THEREOF; MEANS CLOSING SAID ONE END OF SAID BORE INCLUDING A LABYRINTHIC METAL DISC AND AN INTERNALLY THREADED CAP ADAPTED FOR THREADED ENGAGEMENT WITH SAID CYLINDER, SAID CAP HAVING AN ORIFICE THEREIN AND AN INTERNAL WALL TAPERING OUTWARDLY THEREFROM AND DEFINING A FRUSTO-CONICAL-SHAPED CAVITY THEREWITHIN, SAID WALL ABUTTING SAID DISC FOR FIRMLY FIXING SAID DISC OVER SAID BORE; MEANS CLOSING SAID OTHER END OF SAID BORE INCLUDING A METAL SEALING DISC IN SAID BORE, AN INTERNALLY-THREADED CAP IN THREADED ENGAGEMENT WITH SAID CYLINDER AND A SPACER RING MOUNTED BETWEEN SAID SEALING DISC AND SAID CAP SO THAT SAID SPACER RING AND SAID SEALING DISC URGE SAID SOLID PROPELLANT MIXTURES AGAINST SAID METAL DISC AT SAID ONE END OF SAID BORE, SAID LAST MENTIONED CAP HAVING AN APERTURE THEREIN; AND IGNITION MEANS FOR IGNITING THE SOLID PROPELLANT MIXTURES INCLUDING A HEAT SENSITIVE IGNITER MATERIAL IN CONTACTING RELATIONSHIP WITH SAID FIRST SOLID PROPELLANT MIXTURE, AN INITIATOR FOR FIRING SAID IGNITER FOR FIRING SAID IGNITER MATERIAL AND MEANS CARRIED BY SAID LAST NAMED CAP IN SEALED ENGAGEMENT WITH THE WALL OF SAID APERTURE IN SAID LAST NAMED CAP FOR ACTUATING SAID INITIATOR; WHEREBY THE SOLID PROPELLANT MIXTURES ARE IGNITED IN SUCCESSIVE ORDER AND THE GASES DEVELOPED FROM THE BURNING THEREOF PASS THROUGH A LABYRINTH PATH IN THE FIRST-MENTIONED DISC, BUILD UP PRESSURE WITHIN THE FRUSTO-CONICAL CAVITY OF THE FIRSTMENTIONED CAP AND ARE DISCHARGED FROM THE ORIFICE THEREIN AS A HIGH-VELOCITY, GASEOUS JET, FIRST HAVING A RELATIVELY HIGH TEMPERATURE AND THEN A RELATIVELY LOW TEMPERATURE.

sited States Patent m1 Phillips [5 PYROJETCUTTER FOR UNDERWATER OR LANDUSE [75] Inventor: Ralph 0. Phillips, Old Saybrook,

Conn. I

[73] Assignee: The United States of America as represented by the Secretary of the Navy [22] Filed: 0ct;30,1963

[21] Appl. No.: 320,239

[52] US. Cl. ..-..;...l02/1 R, 86/1 A, 102/90 [51] Int. Cl ..-.F42b'33/06 [58] Field of Search ..89/l; 102/9, 1, 39, 24, 90; 86/1, 1 A; 148/9; 266/23;'149/38 [56] References Cited UNITED STATES PATENTS 2,059,717 11/1936 Trimback "89/3713.- 2,391,242 12/1945 l-lurrey ..l02/90 2,747,856 5/1956 B urdwood ..26 6/23F 3,054,349 9/1962 Plumley ..l02/1 3,108,918 10/1963 Plumley.... .....86/l'X 3,117,518 l/l964 Porter 102/24 Primary Examiner samuel W. Engle Attorney-Q. B. Warner and R. F. l-lossfeld EXEMPLARY CLAIM 1. An apparatus for burning through explosive containing cases and for melting out the enclosed explosive comprising a metal cylinder having a bore along burns to produce a relatively high-temperature gaseous product positioned in said bore at one end thereof;

a second combustible solid propellant mixture which burns to produce a relatively lowtemperature gaseous product positioned in said bore at the other end thereof;

- means closing said one end of said bore including a labyrinthic metal disc and an internally threaded cap adapted for threaded engagement with said cylinder, said cap having an orifice therein and an internal wall tapering outwardly therefrom and defining a frusto-conical-shaped cavity therewithin, said wall abutting said disc for firmly fixing said disc over said bore; means closing said other end of said bore including a metal sealing disc in said bore, an internallythreaded cap in threaded engagement with said cylinder and a spacer ring mounted between said sealing disc and said cap so that said spacer ring and said sealing disc urge said solid propellant mixtures against said metal disc at said one end of said bore, said last mentioned cap having an aperture therein; and ignition means for igniting the solid propellant mixtures including a heat sensitive igniter material in contacting relationship with said first solid propellant mixture, an initiator for firing said igniter for firing said igniter material and means carried by said last named cap in sealed engagement with the wall of said aperture in said last named cap for actuating said initiator; whereby the solid propellant mixtures are ignited in successive order and the gases developed from the burning thereof pass through a labyrinth path in the first-mentioned disc, build up pressure within the frusto-conical cavity of the first-mentioned cap and are discharged from the orifice therein as a high-velocity, gaseous jet, first having a relatively high temperature and then a relatively low temperature.

4 Claims, 4 Drawing Figures PATENTEU R3 I973 INVENTORS Ralph 0. Phi/lips W ATTORNEY PYROJ ET CUTTER FOR UNDERWATER R LAND USE a The present invention relates to the melting or burning of metal, and more particularly to an apparatus for producing a high-velocity, high-temperature jet that may be employed for. any metal cutting or perforating operation, either underwater or in air.

Heretofore, it has been proposed to employ metal powder as a fuel for a blow torch for cutting through metal and the like. In such apparatus the powdered metal, mixed with oxygen or with a fuel gas, is burned at the torch tip to provide a hot flame. The operation of such torches requires that the metal powder be carried in the gas stream and this involves difficulties in securing uniform dispersion of the metal powder, and involves complicated equipment to proportion the powder and gas and to prevent flash back.

In the present invention a modified pyrotechnic or propellant mixture is enclosed in a small casing, which may be hand-held or mounted, to develop a high-temperature jet through an orifice at a high velocity which not only melts but also erodes metals by a combination of heat and a scouring-away action. As such, the apparatus of the present invention is designed to provide a relatively small exothermic burning charge to melt through an explosive containing case either underwater or above water. The invention, however, is not limited to the use of burning through a metal explosive containing case, but rather it may be employed just as well for any metal burning or cutting operation either underwater or in the air, such as an underwater grommet cutter, an underwater cable cutter, an underwater mine flotation chamber perforator, or any of these and other similar uses on land in open-air.

Although somewhat related small gas generator devices have been produced in the past for maintaining a pressure in a missile s servo-mechanism, filling rubber life rafts with the products of combustion, inflating rubber pontoons on aircraft, etc., all such endeavor has been to produce a gas as low in temperature as possible so as not to deteriorate the rubber or have too much loss of pressure due to cooling. The present invention uses a mixture or mixtures, depending on the use of the pyrojet, with very much higher temperatures, in fact in some cases, as high as possible. i

A primary object of the present invention is to provide a new and improved apparatus for cutting metal or other material either underwater or on land.

A further object is to provide a new and improved device for melting through explosive containing cases, either underwater or above water.

Another object is to provide a new and improved device for burning through explosive containing cases and for melting out or deactivating the enclosed explosive.

Still another object of the present invention is to provide an apparatus of relatively simple construction, which may be either hand-held or mounted during operation, for cutting metal or other material, either underwater or on land in the open-air.

According to the present invention a modified pyrotechnic or propellant composition is enclosed in a small casing and upon ignition develops a high temperature, high velocity jet which exits the casing jet through an orifice in one end of the casing. The cutting or perforating is accomplished by melting or burning so that the temperature of the high-velocity burning jet must be at or above the melting point of the metal or at or above the combustion point of the combustible material within the cutter. The pyrotechnic or propellant mixture is ignited at the orifice end of the casing by any appropriate means. The mixture or composition may be fast burning or relatively slow burning depending on the type of work to be done. In the case of the burning out of an explosive charge in an explosive containing case, such as a limpet or bomb, wherein the charge comprises a combustible but essentially insensitive to thermal detonation material, they composition employed must be one that will provide a sufficient period of burning to insure jet-flame activation of the explosive charge adequate to cause continued burning or deactivation thereof until it is wholly or partly consumed. Another factor determining the specific composition to be used in the pyrojet cutter is that of the cutting temperature required.

This invention also contemplates a melting-out procedure, and in this case the pyrojet cutter may also include a low-temperature burning charge. When this procedure is employed, a high-temperature jet is first used to gain admission through the metal of the explosive containing case, by perforating the case in one or more places, and this is followed by the low-temperature jet which melts out or deactivates the enclosed explosive material, the temperature in such instances being low enough not to cause ignition of the explosive, but only deactivation thereof.

The burning jet of the novel pyrojet cutter contemplated in this invention develops when the gas emanating from the ignited composition or mixture escapes at a high velocity through the orifice at one end of the easing. Small pyrojet charges may be held in the hands of the operator in a specially designed frame, while the larger charges are held in a special device which may be attached to the object being cut, perforated or burned out, as the case may be. The latter fixed-type devices provide means for firmly attaching the cutter to the object or to the surrounds, such as the ships hull so as to withstand the thrust generated by it and to insure maintenance of the correct stand-off. It is further contemplated that the thrust may be neutralized by means of a retro-thrust device built into the cutter.

In the accompanying drawing there is shown a preferred construction of the novel pyrojet cutter. The obvious utility and the many attendant advantages of this invention will be readily appreciated as the same becomes more fully understood from reference to the following detailed description when considered in connection with the drawing, wherein:

FIG. 1 is a longitudinal sectional view of a device in accordance with a preferred embodiment of .the invention;

FIG. 2 is a perspective view of the device supported by one of the special holding devices; 7

FIG. 3 is a perspective view illustrating the device supported by another special holding device; and

FIG. 4 is a perspective view of a modified orifice cap for use with the present invention.

Referring now to the drawing, wherein like reference characters designate like or corresponding parts throughout the several views, and more particularly to FIG. 1 thereof, the reference character 10 generally designates the device of the present invention comprising a tubular casing 1 1 composed of any material suitable for the purpose such, for example, as cast iron, carbon steel or aluminum. The casing 11 is externally threaded at each end as at 12 and 13 for threaded engagement with caps 14 and 15, respectively, providing end closure means for the casing, the caps being composed of the same or similar material as the casing.

Within the bore 16 extending through the casing 11 there is contained a combustible solid material generally designated by the reference character 17, and shown more specifically in FIG. 1 as comprising two separate charge mixtures 18 and 19. The mixture 18 is a high-temperature burning charge, used in the present invention during metal cutting operations, and it will be referred to hereinafter as the metal cutting charge. The mixture 19 is a low-temperature burning charge, used in the melting-out or deactivation of an explosive material through perforations cut in the explosive containing case. Hereinafter the mixture 19 will be referred to as the steaming or deactivating charge.

The steaming and cutting charges have been pressed or molded into prescribed shapes, the former as a cylinder and the latter tubular. They are positioned adjacently within the bore 16 of casing 11 by means of a spaced sealing disc 20 at one end and a thin metal disc 21 such as, for example, an aluminum disc at the other end. The sealing disc 20 is spaced from the one end of the casing 11 by a spacer ring 22 that is urged inwardly of the bore 16 upon the screwing of cap onto the casing 11 and the metal disc 21 is held fast against the other end of casing 11 by the cap 14, which has a tapered inner diameter 23, whereby the cutting and steaming charges 18 and 19, respectively, are urged into abutting relationship against the cap-biased metal disc 21 whenever the cap 15 is secured to the casing 11.

The cap 15 is provided with a bore 24 extending therethrough in which is arranged a suitable plug 25 in sealing engagement with the wall defining the bore. The plug may be made of any insulator material such, for example, as a phenolic, or Kovar glass, depending upon the design. Plug 25 has a pair of electrical leads 26 extending therethrough which are connected from any suitable power supply (not shown) to a squib initiator 27 which is positioned in the bore 28 defined by the tubular cutting charge 18.

The cap 14 at the other end of casing 11 is hollowed out in a truncated-like fashion providing not only an interior surface against which the metal disc 21 abuts when the cap 14 is screwed onto the casing, but also defining a cavity 29. A small orifice 30 in the end of cap 14 aligned with the longitudinal axis of casing 11 when assembled provides communication from the cavity 29 exterior of the device.

Closely positioned to the squib initiator 27 in the bore 28 of metal cutting charge 18 is a special pyrotechnic paper 31 containing a first fire material, such as, for example, a zirconium-barium chromate impregnated on a glass wool mat or any other suitable heat sensitive igniter material, which burns readily to produce extreme heat and insure successful ignition of the cutting charge surrounding it.

In operation, when sufficient electrical energy is passed through leads 26 the squib initiator 27 is actuated, setting fire to the adjacent pyrotechnic paper 31.

This in turn ignites the metal cutting charge 18. The gases formed by the burning operation of cutting charge 18 find their way through a labyrinth path in the metal disc 21, accumulate or build up pressure in the cavity 29 and are discharged from the device through orifice 30. It can be readily seen that the discharged gas takes the form of a high-velocity, high-temperature jet which is adaptable for burning or cutting through metal.

When employed to cut through explosive containing cases, where it is desirable to further melt out the enclosed explosive, as referred to hereinbefore, ignition of the slower, low-temperature burning steaming charge 19 follows that of cutting charge 18, and the ensuing jet becomes less hot.

It should be apparent, however, that the use of only one combustible solid material in the pyrojet cutter is also contemplated by the instant invention in cases, for example, where the operation is one merely of cutting or perforating metal, or one merely of burning or melting out explosives.

Other methods of ignition are also contemplated, including for example, pyrotechnic fuze and water activated battery ignition in place of the electrical ignition described herein.

Reference is now made more specifically to FIGS. 2 and 3 which illustrate some of the special holding devices designed for use with this invention for attaching it to the object being cut or the surroundings adjacent to it.

The holding device generally designated by the reference character 32 in FIG. 2 includes a U-shaped frame in which the legs of the U-frame each comprises an L-shaped bracket made up of integrally formed flat plates 33 and 34. Pivotally fixed to each plate 34 on the side interior of the U-frame and closely adjacent the open end thereof is a slotted arm member 35. The slot is designated by the reference numeral 36. Pivotally fixed to each plate 34 on the side exterior of the U- frame and closely adjacent the base thereof is another arm or linking member 37, the other end of which is attached to arm 35 through a connection at slot 36. This connection comprises a cross-arm 38 cylindrical at least at its ends and extendingbetween the parallel arms 35. The cylindrical ends of arm 38 are reduced in cross-sectional area so they may pass through the slots 36 in arms 35 and through apertures 39 in the linking arms 37 and they are adapted for threaded engagement with nuts 40 for fastening the arms 35, 37 and 38 in any desired fixed relationship.

The center portion of cross-arm 38 is provided with an annular clamping member 41 which may be attached to the arm by welding or any other suitable means. The pyrojet cutter 10 is mounted within the annular clamp 41 and held fast in any desired stand-off position by a wing-screw 42.

The holding device 32 may be attached to the object being cut or perforated by fixing the plates 33 to the object or adjacent to it by any suitable means such, for example, as screw means. For this purpose the plates 33 could readily be provided with threaded apertures of any desired number.

Referring now to FIG. 3 wherein the holding device comprises a clamping unit 41' for setting the pyrojet cutter in the correct stand-off position, a second clamping unit 43 for fixing the angular relationship of the cutter to the object being cut, and three supporting curved legs 44 adapted for attachment to the object being cut. The legs 44 are provided with flanged portions 45 adapted for attachment to the object being cut or to adjacent surroundings by any suitable means (not shown), such as studfgun connectors, underwater adhes'ive means, magnetic feet or screw connectors.

The clamping unit 43 consists of an annular member 46 having three fiat rods 47 welded thereto and extending radially from the center thereof, adapted for attachment to the legs 44 by means of wing screws 48 and screw-nut fasteners 49. Annular member 46 is provided with wing screws 50 for holding the clamping unit 41 in position when assembled.

Clamping unit 41 is similar to the clamping member 41 shown in FIG. 2 except that the unit is comprised of a sphere having a'bore therethrough for receiving the pyrojet cutter, providing a spherical outer surface for gyratory movement in the untightened clamping unit 43. Unit 41' is provided with a flanged portion 51 having wing screw 42 for binding the pyrojet cutter in the desired stand-off position.

It is readily apparent that the special holding devices referred to herein provide adequate means for fixing the pyrojet cutter to the object being cut or adjacent to it for establishing any desired angular relationship between the cutter and the object, and for maintaining the cutter a proper distance from the object.

The cap 14' shown in FIG. 4 is a modified version of cap 14, shown in FIG. 1. Cap 14 contemplates having a plurality of orifices 30, permitting the cutting device of the present invention to directly heat a larger area of material at the same position of stand-off.

The pyrotechnic charges which are used in the pyrojet cutter are of-two main types. These charges may be fast burning or slow burning, as the case may be, and their specific formulations depend on the precise operation contemplated such as, for example, metal cutting and explosive burning or melting.

Irrespective of whether the charge is to be of the fast burning or slow burning type it has, as primary ingredients, from about to about 25% Mg powder by weight, from about 10% to about 25% A1 powder by weight and from about 40% to about 65%BaNO by weight. Modification of the basic composition, depending on whether a fast burning orslow burning charge is desired, is accomplished bythe incorporation of additives.

In the case of a fast bumingcharge the composition, in addition to Al powder, Mg powder and BaNO may contain about 0-5 percent nitrocellulose by weight, about 0-5 percent graphite by weight and about 0-5 percent gilsonite by weight. For example, the following specific composition has been found suitable to penetrate '15 inch thick steel plate:

9.8 grams Mg powder 9.8 grams A1 powder 30.5 grams BaNO 1.8 grams nitrocellulose 1.0 grams graphite [f the charge is to be of the slow burning type it will contain, in addition to Al, Mg and BaNO about 30-45 percent by weight of a polymerizable epoxide resin. Epoxide resins are amine-cured polymers formed by the'reaction of epichlorohydrin with bis (4-hydroxyphenyl) dimethylmethane.

The following specific composition was used to ignite and burn out explosives:

35 grams Mg powder 35 grams Al powder 130 grams BaNO grams epoxide resin In order to provide for the low-temperature melting out of explosives, the foregoing charge may be varied as follows:

20 grams Mg powder 15 grams A1 powder grams BaNO 90 grams epoxide resin The exact formulation of the pyrotechnic charges disclosed herein depends upon their specific use and must, of course, be varied as circumstances indicate.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An apparatus for burning through explosive containing cases and for melting out the enclosed explosive comprising a metal cylinder having a bore along the longitudinal axis thereof, said cylinder being externallythreaded at each of its ends:

a first combustible solid propellant mixture which burns to produce a relatively high-temperature gaseous product positioned in said here at one end thereof;

a second combustible solid propellant mixture which burns to produce a relatively low-temperature gaseous product positioned in said how at the other end thereof;

means closing said one end of said boreincluding a labyrinthic metal disc and an internally threaded cap adapted for threaded engagement "with said cylinder, said cap having an orifice therein and an internal wall tapering outwardly therefrom and defining a frusto-conical-shaped cavity therewithin, said wall abutting said disc for firmly fixing said disc over said bore;

means closing said other end of said bore including a metal sealing disc in said bore, an internallythreaded cap in threaded engagement with said cylinder and a spacer ring mounted between-said sealing disc and said cap so that said spacer ring and said sealing disc urge said solid propellant mixtures against said metal disc at said one end of said bore, said last mentioned cap having an aperture therein;

and ignition means for igniting the solid propellant mixtures including a heat sensitive igniter material in contacting relationship with said first solid propellant mixture, an initiator for firing said igniter material and means carried by said last named cap in sealed engagement with the wall of said aperture in said last named cap for actuating said initiator; I

whereby the solid propellant mixtures are ignited in successive order and the gases developed from the burning thereof pass through a labyrinth path in the first-mentioned disc, build up pressure within the frustooconical cavity of the first-mentioned cap and are discharged from the orifice therein as a high-velocity, gaseous jet, first having a relatively high temperature and then a relatively low temperature.

2. An apparatus according to claim 1 including means for attaching said cylinder in a predetermined selected position with respect to the metal to be burned through comprising means for selectively setting the cylinder at a predetermined angle of inclination with respect to a surface of said metal,

means for locking said cylinder in said predetermined angular setting,

means for selectively varying the distance separating said cylinder-cap orifice and said metal to be burned through,

and means for locking said cylinder in the selected position at a given distance of separation.

3. The device as set forth in claim 1 wherein the hightemperature burning solid propellant mixture comprises from about 10 percent to about 25 percent magnesium powder, from about 10 percent to about 25 percent aluminum powder, from about 45 percent to about 65 percent barium nitrate, about 3 percent nitrocellulose and about 2 percent graphite.

4. The device as set forth in claim 1 wherein the lowtemperature burning solid propellant mixture comprises from about 10 percent to about 25 percent magnesium powder, from about 10 percent to about 25 percent aluminum powder, from about 40 percent to about 60 percent barium nitrate and from about 30 percent to about 45 percent epoxide resin. 

1. AN APPARATUS FOR BURNING THROUGH EXPOSIVE CONTAINER CASE AND FOR MELTING OUT THE ENCLOSED EXPOSIVE COMPRISING A METAL CYLINDER HAVING A BORE ALONG THE LONGITUDINAL AXIS THEREOF, SAID CYLINDRICAL EXTERNALLY-THREADED AT EACH OF ITS ENDS, FIRST COMBISTIBLE SOLID PROPELLANT MIXTURE WHICH BURNS TO PRODUCE A RELATIVELY HIGH-TEMPERATURE GASEOUS PRODUCT POSITIONED IN SAID BORE AT ONE END THEREOF, A SECOND COMBUSTIBLE SOLID PROPELLANT MIXTURE WHICH BURNS TO PRODUCE A RELATIVELY LOW-TEMPERATURE GASEOUS PRODUCT POSITIONED IN SAID BORE AT THE OTHER END THEREOF, MEANS CLOSING SAID ONE END OF SAID BORE INCLUDING A LABYRINTHIC METAL DISC AND N INTERNALLY THREADED CAP ADAPTED FOR THREADED ENGAGEMENT WITH SAID CYLINDER, SAID CAP HAVING AN ORIFICE THEREIN AND AN INTERNAL WALL TAPERING OUTWARDLY THEREFROM AND DEFINING A FRUSTO-CONICAL-SHAPED CAVITY THEREWITHIN, SAID WALL ABUTTING SAID DISC FOR FIRMLY FIXING SAID DISC OVER SAID BORE, MEANS CLOSING SAID OTHER END OF ASID BORE INCLUDING A METAL SEALING DISC IN SAID BORE, AN INTERNALLY-THREADED CAP IN THREADED ENGAGEMENT WITH SAID CYLINDER AND A SPACER RING MOUNTED BETWEEN SAID SEALING DISC AND SAID CAP SO THAT SAID SPACER RING AND SAID SEALING DISC URGE SAID SOLID PROPELLANT MIXTURES AGAINST SAID METAL DISC AT SAID ONE END OF SAID BORE, SAID LAST MENTIONED CAP HAVING AN APERTURE THEREIN, AND IGNITION MEANS FOR IGNITING THE SOLID PROPELLANT MIXTURES INCLUDING A HEAT SENSITIVE IGNITER MATERIAL IN CONTACTING RELATIONSHIP WITH SAID FIRST SOLIF PROPELLANT MIXTURE, AN INITIATOR FOR FIRING SAID IGNITER FOR FIRING SAID IGNITER MATERIAL AND MEANS CARRIED BY SAID LAST NAMED CAP IN SEALED ENGAGEMENT WITH THE WALL OF SAID APERTURE IN SAID LAST NAMED CAP FOR ACTUATING SAID INITIATOR, WHEREBY THE SOLID PROPELLANT MIXTURES ARE IGNITED IN SUCCESSSIVE ORDER AND THE GASES DEVELOPED FROM THE BURNING THEREOF PASS THROUGH A LABYRINTH PATH IN THE FIRST-MENTIONED DISC, BUILD UP PRESSURE WITHIN THE FRUSTO-CONICAL CAVITY OF THE FIRST-MENTIONED CAP AND ARE DISCHARGED FROM THE ORIFICE THEREIN AS A HIGH-VELOCITY, GASEOUS JET, FIRST HAVING A RELATIVELY HIGH TEMPERATURE AND THEN A RELATIVELY LOW TEMPERATURE.
 2. An apparatus according to claim 1 including means for attaching said cylinder in a predetermined selected position with respect to the metal to be burned through comprising means for selectively setting the cylinder at a predetermined angle of inclination with respect to a surface of said metal, means for locking said cylinder in said predetermined angular setting, means for selectively varying the distance separating said cylinder-cap orifice and said metal to be burned through, and means for locking said cylinder in the selected position at a given distance of separation.
 3. The device as set forth in claim 1 wherein the high-temperature burning solid propellant mixture comprises from about 10 percent to about 25 percent magnesium powder, from about 10 percent to about 25 percent aluminum powder, from about 45 percent to about 65 percent barium nitrate, about 3 percent nitrocellulose and about 2 percent graphite.
 4. The device as set forth in claim 1 wherein the low-temperature burning solid propellant mixture comprises from about 10 percent to about 25 percent magnesium powder, from about 10 percent to about 25 percent aluminum powder, from about 40 percent to aBout 60 percent barium nitrate and from about 30 percent to about 45 percent epoxide resin. 